Dehydrogenating hydrocarbons



Patented June 2, 1931 UNITED STATES PATENT emce- MABION' IB. HOPKINS, 0F ELIZABETH, NEW JERSEY, ASSIGNOR TO STANDABD 'OIII DEVELOPMENT COMPANY, .A COBPORA'IION- O1 DELAWARE DEEYDROGENATING HYDEOGABBONS 11o Drawing.

necessitating interruption in the run for al-' lowing necessary cleaning. Moreover the stock used must be selected of higher car-' bon atom number per molecule than the product in view, andit is diflicult to control the extent of cracking down to just the point necessary to secure the maximum yields of the products expected.

In accordance with the present invention,

' instead of yrolytically decomposing hydrocarbons of igher carbon atom number, I proceed to remove hydrogen to the extent desired from h drocarbons of the general range of the nal product intended, and I have discovered that'each hydrocarbon has its own optimum treating temperature, the temperature varying inversely with the molecular weight or boiling point, or more explicitly the structure. That is, the lower hydrocarbons require a higher treating temperature than those of higher carbon atom numher, or structure. For example, propane is treated best at about 440 (3., butane at about 410 C., and on up the series; the optimum treatin temperature becoming lower and lower, y sli htly decreasing diiierentials. This feature ecomes of very great importance where it is desired to treat mixtures of hydrocarbons, as with a knowledge of the boiling curve or the constituents of the mixture it immediately becomes possible to treat the mixture rationally. As hydrogen-removing agent I use oxygen either pure or with a diluent as desired, ordinarily air being the most convenient form. According to the amount and manner of supplying the oxygen, the dehydrogenation can be carried to any extent desired, and compounds with Application filed July 31, 1923. Serial No. 654,947-

one double bond or more than one can be produced.

For the production of compounds having one double bond the amount of oxygen repressure advisably will be maintained low; I

and in t is case also Generally, however,

as diluents, inert gases, steam, etc, may be used. I All of the oxygen may be introduced at once or the oxygen feed may be divided over several successive points of introduction in the treating apparatus. The latter proced-' ure is generally preferable as it facilitates close temperature control.

In starting, the apparatus is initially heated to the proper temperature. If tubes are used this heating may be done by electric means or by furnace heat. If a refractory checker-like chamber be used it may be brought up to temperature by suitable heating ues, somewhat as in gas practice. Generally I or by an initial combustion blast prefer the tubes, as allowing a smoothly operating continuous rocess, and I arran e the hydrocarbon fee 'at the end and t e oxygen or air feed inlets at intervals alon the tubes. After the reaction is started the heat. produced is such that if external heat is required it is necessary only as a deficienc make-up 'to be .used regulatively. Where an is fed at successive intervals along the tubes, it is in some cases advantageous, by reason of the increasing dilution from the accumulating. nitrogen, to use pure oxygen at the final feed points.

Operating pressures. ordinarily will be in the neighborhood of atmospheric, although in some cases, if desired, higher pressures 'may be used, or in some cases, as for in-' stance with high molecular compounds and re'ferably introduced into the treating c amber in vapor phase, or at least it should vaporize shortly after introduction, to get good results.

In treating pro ane,'for example, to repare propylene, t e as is subjected to eat at a temperature 0 440 C., or at least between 410 and 470 0., and air is supplied in'the proportion of about 2 or 3 parts, conveniently 2.5 arts by volume, to each part of hydro'car on. .By introducing the air at successive points the temperature may be regulated more exactly. In treating butane, the temperature is maintained at about 410 0., or at least between 380 and 440 C. At natural gas gasoline plants, various mixtures of propane, etc., or butane, etc., are available, such as vent gases, etc., and these can be readily determined as to composition and treated in accordance with my invention; the temperature in. the first zone being gauged for the highest hydrocarbon constituent and graduated up for the successively lower h drocarbons in the series to be affected. In ehydrogenating a mixture of hydrocarbons such as the gasoline fraction 0 a petroleum distillate, I ordinarily start the reaction at about 265 C. and maintain radually increasing temperature zones t rou hout the length of the reaction chamber. treating a mixture of hydrocarbons such as the kerosene fraction, the temperature of the first zone will be correspondingl lower than that of the first zone for the 'ghter gasoline hydrocarbons. In general, when treating kerosene stock, the temabout 250 perature range usually employed, accordin to this invention,is between 250 C. an

it-will be understood that changes may be made which come within the spirit and scepe of the invention.

. claim: 1. A rocess for partially dehydrogenating by rocarbons, comprising causing the hydrocarbons as vapors to traverse an elongated path in admixture with free oxygen, eating the admixture of hydrocarbon vapors and oxy en to a temperature between 250 C. and 4 0 0., the quantity of oxygen beingiso limited as to partially dehydrogento t e hydrocarbons, thereby forming unrature' ma increase progressively from pe to about 400 C. The temile I have described my mvention by reference to certain illustrative details,

a gas containing free oxygen is admitted to the dehydrogenation zone in proportion of about 1 atom of oxygen for every two atoms of hydrogen to be removed from the hydrocarbon. a

3. A process according to claim 1 in which about 1% atoms of oxygen are admitted to the dehydrogenation zone for each hydrocarbon molecule heated,

4. A process according to claim 1 in which air is admitted to the dehydrogenation zone at a plurality of points.

5. A process for selectivel deh drogenating a mixture of saturated hy rocarbons, comprising passing the hydrocarbon mixture in vapor form through a plurality of dehydrogenation zones at progressively higher temperatures between 250 and 470- 0., supplying gas containin free oxygen to pass 1n admixture with t e hydrocarbon vapors through each zone, the quantity of oxygen being so limited as to partially dehydrogenate the hydrocarbons, thereby forming unsaturated compounds without substantial quantities of com ounds containing the three elements .car on, hydrogen, and oxygen, and withdrawing the unsaturated product.

6. A process according to claim 5 in which the quantity of oxygen supplied to each zone 1s not greater than 1 atom of oxygen for each two atoms of hydrogen to be removed in each zone.

7. A process accordin to claim 5 in which air is supplied to the de ydrogenation zones at a plurality of Xoints.

M RION B. HOPKINS.

# saturated compounds without substantial uantities of compounds containin 31m elemente,'car on, hydrogen an gen, and

product.

oxy-

the

withdrawing the unsaturated "2. 'Aprocessaecordingtoclaimlinwhich 

